Inter-Rater Reliability of Ultra Sound Based Rectus Abdominis Thickness Following Blood Flow Restriction Training

August 5, 2026 updated by: Riphah International University

Inter-Rater Reliability of Ultra Sound Based Rectus Abdominis Thickness Following Blood Flow Restriction Training : A Retrospective Analysis.

Accurate assessment of skeletal muscle morphology is important in sports physiotherapy, exercise rehabilitation, and research. B-mode ultrasonography is a non-invasive and accessible method for assessing muscle thickness; however, ultrasound-based measurements may be influenced by image acquisition, anatomical landmark identification, and operator-dependent measurement procedures. Establishing inter-rater reliability is therefore essential to determine whether different assessors can obtain consistent measurements of muscle thickness from the same ultrasound images. The rectus abdominis is an important component of the abdominal musculature and contributes to trunk stabilization and functional performance during exercise. Blood flow restriction (BFR) training has gained increasing attention as a low-load exercise strategy for promoting muscular adaptations, although research has predominantly focused on peripheral limb muscles. Therefore, this study aims to evaluate the inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurements following a standardized BFR training protocol using ImageJ software. Establishing reliable measurement of rectus abdominis thickness will provide a methodological basis for future research investigating abdominal muscle morphology and adaptations in sports physiotherapy, exercise rehabilitation, and BFR-based training.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Detailed Description

A retrospective methodological reliability study design will be employed to evaluate the inter-rater reliability of ultrasound-based measurements of rectus abdominis muscle thickness following a standardized blood flow restriction (BFR) training protocol. The study will utilize previously collected B-mode ultrasound images obtained from healthy young adult male participants who completed the original BFR training protocol. The existing dataset will be reviewed according to predefined eligibility criteria, and only ultrasound images of sufficient quality for identification and measurement of the rectus abdominis muscle will be included in the analysis.

The original BFR training protocol involved low-load resistance exercise performed under blood flow restriction. During the intervention, pneumatic cuffs were applied to the limbs, and participants performed a standardized squat exercise protocol at a low percentage of one-repetition maximum with prescribed repetitions and rest intervals. Ultrasound images of the rectus abdominis obtained according to the standardized imaging protocol will be analyzed retrospectively. The rectus abdominis was selected because it is a superficial abdominal muscle that can be visualized using B-mode ultrasonography and has relatively well-defined anatomical boundaries, allowing its thickness to be assessed using a standardized measurement procedure. Furthermore, the rectus abdominis contributes to trunk stabilization during functional and resistance exercises.

Ultrasound images will be analyzed using ImageJ software. Two independent raters will perform the measurements of rectus abdominis muscle thickness using the same standardized measurement protocol. The raters will independently identify the anatomical boundaries of the rectus abdominis and obtain linear thickness measurements from the ultrasound images. The use of a single standardized image-analysis platform and identical measurement procedures for both raters will minimize variability related to software and measurement techniques. The primary outcome will be the rectus abdominis muscle thickness measured in millimeters (mm).

Inter-rater reliability will be assessed using the Intraclass Correlation Coefficient (ICC) with a two-way random-effects model for absolute agreement and single measurements [ICC (2,1)], reported with the corresponding 95% confidence interval. ICC values below 0.50 will be interpreted as poor reliability, values from 0.50 to 0.75 as moderate reliability, values from 0.75 to 0.90 as good reliability, and values above 0.90 as excellent reliability. Absolute reliability and measurement error will additionally be assessed using the Standard Error of Measurement (SEM) and Minimal Detectable Change at the 95% confidence level (MDC95), where appropriate. Bland-Altman analysis will be performed to evaluate systematic differences and limits of agreement between the two raters. All statistical analyses will be conducted using SPSS, with the level of statistical significance set at p < 0.05.

If the ultrasound-based rectus abdominis thickness measurement demonstrates good to excellent inter-rater reliability, the findings will support the reproducibility of the standardized measurement protocol and its application in future research involving abdominal muscle morphology. The study may provide a methodological foundation for future investigations examining changes in abdominal muscle morphology following BFR and other exercise interventions, with potential relevance to sports physiotherapy, rehabilitation, and exercise science.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
50

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Contact Backup

  • Name: Dr Saad Rauf, PhD
  • Phone Number: 03325957732

Study Locations

  • Pakistan
      • Islamabad, Pakistan, 44000
        • Recruiting
        • Faculty of Rehabilitation for Data Collection and Research Work
        • Contact:
          • Muhammad Haris
          • Phone Number: 03437181808

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Non Athletes

Description

Inclusion Criteria:

  • Recreationally Active

Exclusion Criteria:

  • Known Musculoskeletal injury

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
Retrospective BFR Cohort
Healthy active male participants who underwent a short-duration blood flow restriction (BFR) training protocol. Pre- and post-training ultrasound images of the rectus abdominis muscle were retrospectively analyzed to assess inter-rater reliability of ultrasound-based muscle thickness measurements.
Group 1
Healthy active male participants assessed before the BFR training program. Baseline B-mode ultrasound images of the rectus abdominis muscle were obtained and used for measurement of muscle thickness.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurement
Time Frame: Baseline (pre-training) and post-training ultrasound images obtained at the completion of the two-week BFR training protocol.
Inter-rater reliability between two independent raters in measuring rectus abdominis muscle thickness from B-mode ultrasound images using ImageJ software.
Baseline (pre-training) and post-training ultrasound images obtained at the completion of the two-week BFR training protocol.

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurement
Time Frame: Pre-training and immediately post-training.
Rectus abdominis muscle thickness
Pre-training and immediately post-training.

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Riphah International University

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Principal Investigator: Saad Rauf, PhD, Riphah International University, Isra University, Islamabad

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
August 4, 2026

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
September 6, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
September 20, 2026

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
August 5, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 5, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
August 10, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
August 10, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
August 5, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
August 1, 2026

More Information

Terms related to this study

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • REC/MS-PT/02569

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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